Why was the west coast of Africa so important to the development of the transatlantic slave trade?

The west coast of Africa benefited from monsoon winds, making trade and travel across the Atlantic more efficient.
The west coast of Africa had long historical connections to Europe, allowing for more trade to occur.
The west coast of Africa’s proximity to the Atlantic Ocean made it easier to transport enslaved people to the Americas.
The west coast of Africa had larger population centers than anywhere else in Africa, making it easier to collect enslaved people.

All of the options mentioned contributed to the importance of the west coast of Africa in the development of the transatlantic slave trade.